NASA`S Contribution to the International Rosetta Mission

The U.S. Rosetta Project: NASA`s Contribution to the International Rosetta Mission

C. Alexander, S. Gulkis, M. Frerking, M. Janssen, D. Holmes California Institute of Technology/Jet Propulsion Laboratory 4800 Oak Grove Dr. Pasadena, CA 91109 818-393-7773 Claudia.J.Alexander@jpl.nasa.gov, [email protected], [email protected], [email protected], [email protected]

J. Burch, A. Stern, W. Gibson, R. Goldstein, J. Parker, J. Scherrer, D. Slater Southwest Research Institute PO Drawer 28510 San Antonio, TX 78228-0510 (210) 522-6223 [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]

S. Fuselier Lockheed Martin Advanced Technology Center Dept. ADCS, Bldg. 255 3251 Hanover St Palo Alto, CA 94304 650-424-3334 [email protected]

T. Gombosi Department of Atmospheric, Oceanic and Space Sciences The University of Michigan 2455 Hayward Street Ann Arbor, MI 48109-2143 734-764-722 [email protected]

Abstract—The International Rosetta Mission was TABLE OF CONTENTS successfully launched on March 2, 2004. NASA's 1. INTRODUCTION ...... 1 contribution to this mission consists of the following three 2. THE U.S. ROSETTA PROJECT ...... 2 hardware experiments: Alice (an Ultraviolet Spectrometer), 3. LAUNCH SUPPORT ...... 5 the Ion and Electron Sensor (IES - a plasma instrument), 4. COMMISSIONING...... 6 and the Microwave Instrument for the Rosetta Orbiter 5. OBSERVATIONS OF COMET C/2002 T7 (LINEAR) ...10 (MIRO), as well as other components. Collectively these 6. SUMMARY OF POST-LAUNCH OPERATIONS ...... 11 elements are known as the U.S. Rosetta Project. In this REFERENCES...... 12 paper we present an overview of the U.S. Rosetta Project. BIOGRAPHY ...... 12 We present and summarize the successful launch and early operations phases of the U.S. Rosetta Project. Finally, an unplanned science target appeared in the form of comet 1. INTRODUCTION C/2002 T7 (LINEAR). Comet Linear was successfully observed by the U.S. Rosetta project on two occasions, The U.S. Rosetta Project stands on the verge of the April 30 and May 17, 2004, by both Alice and MIRO.12 transition to Mission Operations. The project consists in part of 3.5 instruments: Alice (an ultraviolet spectrometer), IES (the Ion and Electron Sensor, a plasma instrument), MIRO (the Microwave Instrument for the Rosetta Orbiter), and the electronics package for one of a pair of spectrometers on the ROSINA instrument called the Double 1 0-7803-8870-4/05/$20.00© 2005 IEEE. Focusing Mass Spectrometer (DFMS). These elements 2 IEEEAC paper #1508, Version 1, Updated October 27, 2004

comprise the NASA hardware contribution to the Following launch a successful series of activities International Rosetta Mission payload. In other commenced to initiate commissioning of the payload. The contributions to the mission, NASA provides key back-up Alice detector door was opened, and first light was navigation and tracking support for the International Rosetta recorded. MIRO, using its chirp transform spectrometer Mission by way of its Deep Space Network (DSN), In (CTS) for the first time, obtained the water signal of the addition, NASA supports an interdisciplinary scientist and Earth, as well as signals from Venus. A sophisticated provides investigator support to Co-Investigator’s (CO-I’s) spacecraft “spiral scan” pointing scheme was worked out on non U.S. payload instruments. and deployed for the first time for the MIRO measurements. IES validated its interface with the power interface unit The International Rosetta Mission is destined to study the (PIU) and conducted successful low-voltage operations. nucleus of comet 67P/Churyumov-Gerasimenko and its The double focusing mass spectrometer conducted environment for a period of 17 months starting in August successful high-voltage operations. This paper discusses the 2014. The near-nucleus phase will begin at a heliocentric first phase of commissioning, as well as anomalies and distance of about 3.25 AU, after which there will be the surprises that were discovered. deployment of a Lander (Philae). The Lander mission will last approximately 2 weeks after which the orbiter will In the middle of commissioning, an unexpected target of conduct observations of both far and close proximity to the opportunity appeared in the form of comet C/2002 T7 nucleus, leading ultimately to passes in which observations (LINEAR). This paper concludes with a description of how may be conducted from as close as 1 km (3280 feet). The scientific measurements were obtained when the spacecraft orbiter will escort the comet through perihelion, to a post- was not fully characterized and what they might mean. perihelion distance of about 2 AU. Because commissioning was not fully complete as of the The prime scientific objective of the Rosetta mission is to writing of this report, the timeframe covered here includes study the origin of comets, the relationship between the months leading up to launch and the first 6 months of cometary and interstellar material and its implications with Rosetta’s cruise from March 2 through August 2, 2004. regard to the origin of the Solar System. The measurements to be made to achieve this are: 2. THE U.S. ROSETTA PROJECT (1) Global characterization of the nucleus, determination of dynamic properties, and surface morphology and NASA’s contributions to the International Rosetta mission composition are the following three U.S. hardware experiments: Alice (2) Determination of the chemical, mineralogical, and (an ultraviolet imaging spectrometer), the Ion and Electron isotopic compositions of volatiles and refractories in a Sensor (IES), and the Microwave Instrument for the Rosetta cometary nucleus Mission (MIRO). A fourth instrument, ROSINA, the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, (3) Determination of the physical properties and is a European investigation with a U.S. hardware interrelation of volatiles and refractories in a cometary contribution consisting of the electronics package. nucleus Specifications of these hardware components are summarized in table 1. Other components of the NASA (4) Study of the development of cometary activity and the contribution to the mission include: the participation of an processes in the surface layer of the nucleus and the interdisciplinary scientist (IDS); backup tracking, inner coma (dust/gas interaction) telecommunications, and navigation assurance provided by the DSN; and support for the scientific participation of U.S. (5) Global characterization of asteroids, including investigators on non U.S. experiments. determination of dynamic properties, surface morphology, and composition Alice

The mission was successfully launched on March 2, 2004. The Alice instrument [1, 2, 3] will obtain spectra of the Back-up tracking and navigation support provided to ESA nucleus and the coma in the 700-2050 Å bandpass (ultra- by NASA’s Deep Space Network (DSN) involved the so violet and extreme ultra-violet wavelength regions). This called Space Link Extension (SLE) services interface investigation will: (1) directly determine the volatilized between the NASA and ESA ground support networks, helium (He), neon (Ne), Argon (Ar), and possibly krypton interleaving two differing cultures of communication and (Kr), and the nitrogen (N2) content of the nucleus in order to ground station equipment. This paper will report on the provide information concerning the temperature of successful mating of different ground networks, and some formation and the thermal history of the comet since its residual issues. formation; (2) directly determine the production rates and

spatial distributions of the key parent species, water (H2O),

carbon monoxide (CO), and carbon dioxide (CO2), thereby scientists a better idea of how comets formed, what they are allowing the nucleus/coma coupling to be observed and made of and how they change with time. interpreted without significant ambiguities; (3) obtain unambiguous atomic budget measurements of carbon, Rosetta Orbiter Spectrometer for Ion and Neutral Analysis hydrogen, oxygen, nitrogen and sulfur in the coma to derive (ROSINA); electronics package for the Double Focusing the elemental composition of the volatile fraction of the nucleus; and (4) study the onset of cometary nuclear activity Mass Spectrometer (DFMS) in ways that Rosetta otherwise cannot. Additional ROSINA is a state-of-the-art mass spectrometer [6] with objectives include (5) mapping the cometary nucleus at far- two redundant sensors using different technologies for UV wavelengths and characterizing the presence of icy UV simultaneous and independent mass detection and absorbers on its surface; (6) studying the photometric verification. The ROSINA instrument is capable of making properties of small grains in the coma as an aid to mass detections to 300 AMU (atomic mass units), and of understanding the size distribution of cometary grains and resolving mass to and accuracy of one in three thousand (on how they vary in time; and (7) mapping the time variability the 1 percent level). The primary measurement objective of of O II, C II, and N II emissions in the coma and ion tail ROSINA is to determine the elemental, isotopic, and around perihelion in order to connect nuclear activity to molecular composition of the atmospheres and ionospheres changes in tail morphology and structure, and coupling to of comets, as well as the temperature and bulk velocity of the solar wind. the gas and the homogeneous and inhomogeneous reactions of gas and ions in the dusty cometary atmosphere and Ion and Electron Sensor (IES) ionosphere. One of the most exciting measurements will be The IES [4] is a plasma instrument consisting of two the carbon dating of the nucleus, or the determination of the 12 13 electrostatic analyzers, one each for electrons and ions. In C /C ratio and the D/H ratios in organic molecules. general, IES acquires ion and electron measurements in 256 ROSINA will also provide gas pressure measurements bins over an azimuth range of 90 degrees and polar angle of important for the health and safety of other instruments, 360 degrees (less spacecraft obstructions). Thus IES notably Alice, which will use ROSINA detections of collects plasma data roughly in 2.8π steradians of space, significant increases in gas flux to close its aperture door. and samples plasma velocity space. The IES will investigate (1) the solar wind interaction with the cometary ROSINA consists of (1) two separate spectrometers, (2) a nucleus, (2) the processes that govern the composition and velocity and temperature sensor and (3) a common data structure of the cometary atmosphere, and (3) the processing unit. The mass spectrometers employ different interaction between the solar wind and the cometary and complementary measurement techniques. The DFMS atmosphere. In addition, the IES will investigate the uses magnetic analysis to achieve high mass resolution and interaction between the solar wind and one or two main-belt high dynamic range. The Reflectron Time of Flight asteroids, with specific objectives related to sputtering and (RTOF) spectrometer uses time of flight analysis to achieve ion implantation, electrical charging of the surface, and high sensitivity over a broad mass range. The velocity and wake effects. temperature sensor determines the flow velocity and temperature of the cometary gas in the coma. The NASA Microwave Instrument for the Rosetta Orbiter (MIRO) hardware contribution to ROSINA consists of a big part of the electronics package for the DFMS sensor. The instrument [5] will obtain spectra of the nucleus and the coma in the microwave region of millimeter wavelengths Deep Space Mission System (DSMS) (190 GHz, ~1.6 mm) and submillimeter wavelengths (562 GHz, ~0.5 mm). This scientific investigation addresses the The Rosetta mission requires telecommunications support nature of the cometary nucleus, outgassing, and for navigation, tracking, and telecom (command and development of the coma as strongly interrelated aspects of telemetry). NASA’s role includes the use of DSN resources cometary physics. MIRO will measure the near-surface for backup and emergency and launch activities. It will also temperatures of at least one asteroid and the comet be utilized during the various critical events: planetary 67P/Churyumov-Gerasimenko, thereby allowing estimation gravity assists an asteroid fly-by, and the final comet of the thermal and electrical properties of these surfaces. In encounter. addition, the spectrometer portion of MIRO will allow measurements of water, carbon monoxide, ammonia, and Interdisciplinary Scientist (IDS) methanol in the gaseous coma of comet 67P/Churyumov- Dr. Paul Weissman is the sole U.S. interdisciplinary Gerasimenko. These measurements will allow study of the scientist for Rosetta. His tasks include modeling and process of icy cometary sublimation (change from the observation of mission targets in support of the science frozen state, ice, to a gas) in time and distance from the sun. planning work of the Science Working Team (SWT or the The data from MIRO, along with data from other ESA analog of what is known on NASA missions as the instruments on the orbiter and the comet lander, will give Project Science Group - PSG). Modeling tasks include

Table 1. Specifications of hardware components in the U.S. Rosetta Project Alice Measured Flight Performance Passband 700-2050 A 4-8 A point source Spectral resolution 8-12 A extended source Spatial resolution 0.05˚ x 0.6˚ Field of view 0.05˚ x 2.0˚ + 0.1˚ x 4.0˚ Mass/power 3.0 Kg / 4 W

IES Measured Flight Performance Energy range 1 eV - 30 keV Energy resolution 4% Field of view 2.8 π steradians Mass/power 1 Kg / 1.85 W

MIRO Measured Flight Performance 190 GHz, ~1.6 mm (millimeter wavelengths) Passband 562 GHz, ~0.5 mm (sub-millimeter wavelengths) Spectral resolution < 100 kHz (sub-millimeter) 75 m (millimeter) Spatial resolution 25 m (sub-millimeter) < 22 arc minutes (millimeter) Field of view < 8 arc minutes (sub-millimeter) Radiometric sensitivity 1 K (continuum) Mass/power 19.9 Kg / 43 W

ROSINA - DFMS Measured Flight Performance Mass range 12- >130 AMU Mass resolution 1200-3650 @ 1% Sensitivity 5 x 10^-6 A/Torr comet nucleus modeling, gas and dust environment Interdisciplinary studies include UV chemical data with modeling, and studies of the comet nucleus composition and thermal IR surface maps such that the resident depth of its relationship with interplanetary, interstellar and volatiles can be revealed, cross-correlation of noble gas circumstellar dust. On April 14-16, 2004, he obtained abundances with those measured by a mass spectrometer photometry of asteroid 2867 Steins, one of the Rosetta flyby but without the mass to charge uncertainty, and thermal IR targets, for use in deriving a precise rotation period for the coma maps combined with UV fluorescence data such that asteroid and for generating a shape model. fluorescence and collision process that are otherwise model dependent can be studied. Investigator Support on non U.S. experiment teams VIRTIS. Support includes contributions towards: full NASA identified 8 U.S. Co-I's on ESA-led Rosetta Orbiter spectro-photometric calibration; establishment and experiments for support. Supported investigations are: modeling of instrument performance, modeling of VIRTIS (Visible and Infrared Thermal Imaging target photometric properties, and instrument Spectrometer), Radio Science, and OSIRIS (Optical, measurement scenario development. Spectroscopic, and Infrared Remote Imaging System). The sole U.S. Co-I on the COSIMA (Cometary Radio Science: Long-term support will include a component Secondary Ion Mass Analyser) experiment passed away addressed to gravity science experiments: (1) on Nov. 21, 2003. Science objectives for these Accumulate dynamical facts about the target object for investigations include definition of post-launch instrument the Rosetta mission; (2) Define the dynamical calibration parameters and instrument spectral sensitivities. problem; (3) Develop an analytical solution, including rotation to first order, and perform numerical tests of 4

the first order theory; and (4) study orbits near any specific mission-critical events, such as launch and early identified resonances, and test for stable orbits. orbit, planetary encounters and deep space maneuvers. Within the scheduling regime at JPL the allocated DSN OSIRIS: Current support includes a subset of instrument backup stations are scheduled as prime. Rationale: Each calibration work, including establishment of the DSN station will be on point and ready to provide temperature dependence of the gain of the CCD output immediate command capability per ESA requirements. amplifiers on the wide and narrow angle cameras, and shape determination of the PSF. The DSN will augment the ESA ground support with telemetry and radiometric data for all allocated passes. DSN command support will occur only at the request of the 3. LAUNCH SUPPORT Rosetta operations manager at ESOC. Nominal tracking support remains a principal responsibility of ESAs New As called for in the mission governing documents, NASA Norcia station. Radiometric data collected from the DSN in supplied telecommunications support in the form of back-up back-up mode will be used to augment the ESA prime tracking and navigation coverage during the launch navigation data types collected from New Norcia, and as activities and through the early operations phase (LEOP). such provide critical support for mission navigation. NASA In many respects, Rosetta was a pioneering mission with is sufficiently satisfied with this definition that it will regard to international collaboration and the use of the DSN become the prototype wording for future mission and other NASA resources in conjunction with foreign Memoranda of Understanding (MOUs) where such support institutions. When the initial commitments were made the is required. complexity of implementing ground support of this kind between two very different agencies was not appreciated. A major component of the agreement to provide cross Moreover, the mission was always to be operated under support for the Rosetta mission that is very import, but strictest constraints in cost. As the use of DSN assets and separate from the availability of DSN resources, is the calculation of navigation solutions is resource rich, NASA interface, which enabled convenient and low cost data was interested in ensuring that the cost of such support did transport services. These services have recently been not become more than the agency could bear. Finally, as included in technical upgrades to the capability of the DSN with all things technical, time produces advances, and have been key to Rosetta support. simplifications, or at least changes in format that must be accounted for. Adjusting for all of these components were DSMS Cross Support Services for Rosetta hidden challenges for the U.S. Rosetta project. The application of Consultative Committee for Space Data Systems (CCSDS) standards [7] applied to the acquisition The Use of JPL’s DSMS in a Back-up Capacity and delivery of telemetry data, and for the radiation of Back-up support was initially defined as a rather vague telecommands for this mission. Two other missions requirement to point a DSN asset at the Rosetta spacecraft currently supported by the DSN, along with Rosetta, have should an occasion arise and/or during specific periods made use of the CCSDS standards known as the Space Link surrounding mission-critical events as a secondary tracking Extension (SLE) interface. Essentially, SLE is an additional mechanism. ESA’s exact requirement was better defined as protocol layer with a common interface such that each “hot back-up”, a term and capability that is obsolete in the participant in the interface might have access to services, era of expanding mission sets and limited resources. The which would normally be specific to the user and/or DSN antenna would be on point, prepared to support the provider organization(s). NASA has been a participant in Rosetta spacecraft but on stand-by, until ESA called for the development of these standards, which greatly simplify tracking support. Given the number of missions the DSN is cross support between agencies. requested to support, it could not provide a service that is principally “hot back-up”. Instead, DSN assets, under such The implementation of SLE used for Rosetta incorporates requirements are scheduled as prime, because the antenna telecommand capability to a DSN station directly from the cannot be used for any other purpose while these ESA mission operations control center. ESA connects to the requirements are being met. Likewise, navigation support scheduled DSN station using what is termed a “bind” was initially defined to be a review of imprecisely defined procedure, which provides authentication and authorization. ESA solutions. NASA had not initially expected to commit Once established, ESA has control of when and how DSN tracking assets for an ESA mission in large blocks of commands are radiated to the spacecraft. The circuits used time as “prime” tracking support. to make the connection are dedicated circuits established specifically for ESA cooperative missions utilizing standard The current definition of back-up support for the Rosetta TCP/IP protocols. In this particular case the circuit is shared project is as follows: The Rosetta Project uses the ESA New with Mars Express because of the commonality of services Norcia station as the principal support station during the and integrated operations. Rosetta mission. DSN provides back-up support for

On the telemetry side, return services are provided to ESA Soon after the launch delay began a search for a new target, through an indirect path. Instead of a connection directly to since a possible delay of a year could not get the spacecraft the ground station tracking Rosetta, telemetry data is to the original target in the right phase, comet orbit sunward transported to JPL via internal circuit and protocols to the months before perihelion, without a different launch multi-mission operations center at JPL. ESA connects to vehicle. When a new target was selected and trajectory dedicated SLE servers within the Advanced Multimission options assessed, it was discovered that the proposed launch Operations Systems (AMMOS) that then provides the return date would have the spacecraft launching in the direction of data services specified by the SLE standard. the sun. This would not normally be a major problem, but ESA starts its missions at S-band during the LEOP phase. Service Management, as a SLE service, has not been Solar noise at S-band effects station performance and implemented and sequence of events planning and degrades the signal to noise ratio of the tracking station. scheduling are accomplished in a simplified mode, using ESA planned on using their 15 meter tracking station at the manual inputs and nominal sequence of events formats for Kourou launch site for most of the LEOP. With station operations. performance significantly degraded by solar noise, the station could not be used past the first few days of LEOP operation. As the launch window slipped, the apparent angle between the sun and the spacecraft decreased The interaction between the ESA Science Operation Center exacerbating the problem. The solution was add an (ESOC) and the DSN was highly successful with Rosetta additional DSN station within the mix to cover the gap [8], more so than with Mars Express, or INTEGRAL - other between the New Norcia station near Perth Australia and ESA missions requiring DSN support that use the same SLE the DSN complex near Madrid Spain. Although similarly services as Rosetta. This situation is attributable to the fact affected by solar noise at S-band, the aperture was more that Rosetta was launched after both INTEGRAL and Mars than double, 34m vs 15m, and provided the margin Express so that most of the interface issues had been necessary for quality telemetry performance. resolved. It would not have been that way except for an Ariane launch failure that preceded the Rosetta launch. As the launch date approached the date and timing of launch Rosetta was originally targeted to comet Wirtanen with a slipped several windows due to high winds at the launch launch date of January 13, 2003. With the postponement of site, and an unusual configuration of Launcher thermal Rosetta’s launch to February 26, 2004, JPL and ESOC had protection detected during a countdown visual inspection. time to resolve a number of outstanding issues, for example, Finally, launch conditions were positive and the spacecraft the distribution of service instance files. The service was launched on March 2, 2004. The ESA station at package that defines how SLE is to be used for each defined Kourou acquired the first downlink S-band signal at track, could not be broadcast to all DSN stations 09:34:51 UTC. The DSN acquired the downlink with 26m simultaneously as is the practice within the DSN with station at Madrid at 09:40:59 UTC for the purpose of initial station configuration data. Each service instance is defined acquisition and predicts updates. Subsequently the 34-m for a particular antenna and separate distribution mechanism station, at Madrid was used to acquire telemetry. The had to be implemented to insure delivery. Without the LEOP phase was extremely successful with now major authenticated service instance file in place, ESA could not anomalies and was officially terminated at 10:05 UTC on make the connection to the assigned station. One other March 5. In fact, Rosetta ground support and spacecraft outstanding issue was the uncertainty in acquiring the operations went so well within the first months that a total spacecraft. The ESA transponder had at least two known of 22 DSN stations were released from the schedule, anomalies and close attention had to be paid to the available to other users. acquisition profile. Originally Rosetta would have launched before Mars Express and would have thoroughly exercised the telecom system in flight. Instead, Mars Express became the in-flight example. Both missions have the exact same transponder. 4. COMMISSIONING

There were further consequences of the Rosetta launch Commissioning for ESA missions has always been different delay. From NASA’s perspective, the new launch date from that for NASA missions in that the followed a very high activity period at Mars, which commissioning/check-out phase nominally lasts 90 days included an armada of spacecraft in orbit and on the surface. rather than the 30 days used in a NASA mission. As an A February 26 launch date, although at the tail end of the added complexity for the Rosetta Project, ESA planned a peak of activity, resulted in significant negotiations for DSN hiatus in Rosetta spacecraft commissioning for Mars resources to insure the Project that it had the antennas it Express orbital operations. ESOC staff were to shift their needed. attention from Rosetta to Mars Express during the summer of 2004. Thus Rosetta commissioning was to take place in two phases. Phase 1 would commence at launch and wind

6 Table 2. Summary of Commissioning Milestones for the U.S. Rosetta Project

Launch ...... March 2, 2004 down in mid-June. Phase 2 would commence in early September and wind down in mid-October. Commissioning, Part 1, Functional Check IES power on ...... March 19, 2004 Aside from instrument turn-on and verification of nominal Alice power on ...... March 26, 2004 modes, voltages, and telemetry, Phase 1 objectives of the MIRO power on...... March 31, 2004 commissioning exercise, for the U.S. Rosetta Project MIRO Venus calibrations ...... April 1, 2004 included the following: (1) Verification of the MIRO beam Alice open detector door...... April 17, 2004 direction, and characterization of the side-lobes of the beam. Alice first light...... April 21, 2004 Beam misalignment is supposed to be minimized by placing MIRO Earth calibration ...... April 24, 2004 the beam nearly parallel at the telescope/optical bench IES low-voltage operations ...... May 9, 2004 interface. Lateral misalignments are supposed to be DFMS HV operations ...... May 21, 2004 minimized by the placing of the telescope mount near the beam axis. (2) Execution of the Alice Performance Alice Performance Aliveness Test (PAT) Aliveness Test (PAT) which provides the instrument ...... May 28, 2004 sensitivity and alignment information needed for mission science data acquisition, and allows for derivation of the Observations of Comet LINEAR instrument effective area curve. (3) Validation of the basic Alice and MIRO ...... April 30, 2004 performance of the ROSINA DFMS with high-voltage Alice and MIRO ...... May 14, 2004 operations. (4) Validate the basic performance of IES with low voltage operations. Additional science functionality, Commissioning, Part 2, Pointing and Interference check-out, and high voltage operations with IES are to be Campaigns conducted in Phase 2 of the commissioning timeframe, as IES HV operations...... Sept 6, 2004 shown in Table 2. Pointing Campaign #1 ...... Sept 11-17, 2004 U.S. Rosetta Commissioning Schedule Interference Campaign #1...... Sept 22-24, 2005 Pointing Campaign #2 ...... Sept 25-28, 2004 IES was the first instrument of the U.S. Rosetta project to Interference Campaign #2...... Oct 12-13, 2005 initiate commissioning activities. With an initial power-up on March 19, 17 days after launch, the entire Rosetta function of wavelength was measured using scans of two Plasma Consortium validated power to the consortium IUE-calibrated UV stars (HD 203245 and HD 218045), instruments and the operation of the power interface unit along with both Kurucz spectral models and IUE-measured (PIU). Low-voltage operations with IES were then flux values at specific wavelengths. With this technique, the postponed until much later in the commissioning schedule total in-flight sensitivity of ALICE in the 1275-1900 Å as the spacecraft entered an unexpected thermal regime. regime was shown to be close to the in-flight expected sensitivity based on earlier ground calibration tests. Alice Phase 1 commissioning took place in three stages. On March 26, Alice powered on for the first time and MIRO Phase 1 commissioning was accomplished in two performed the following: verification of the prime and stages. On March 30, MIRO powered on for the first time redundant power, C&DH interfaces, aperture door and performed exercise of all modes and of the calibration unlatching and then operations (initial opening, plus 12 mirror. In this phase, engineering data were nominal, repeated cycles), microprocessor context save and restore including currents, voltages, and temperatures; receiver functions, heater performance tests, a broad suite of gains matched laboratory measurements; noise sensitivities memory checksums, and testing of detector electronics. met or were slightly better than in the laboratory; and The April 15-24 dates contained the bulk of Alice spectroscopic spectra appeared normal. The next day the commissioning activities. During this time, Alice opened beam direction was calibrated with spiral scans around the detector door, performed ramp-up tests of the high- Venus. On April 30, goals accomplished included 1) voltage power supply, executed detector performance tests validation of pointing, 2) verifying end-to-end spectroscopic (dark count and response), executed software performance capability by observing the ground state transition of water tests, and obtained a first-light image of the hydrogen at 557 GHz in the Earth's upper atmosphere, and 3) background emission. The PAT was canceled, a few hours verification that the commands for the CTS heater were before it was scheduled to begin on the last day, due to implemented correctly in the command database in response spacecraft thermal problems (see page 9, IES Temperature to the Venus CTS anomaly (next section). discussion).

The PAT test, rescheduled to a special slot very late in the Phase 1 commissioning, produced the first measurement of the in-flight effective area of ALICE at wavelengths between ~1275-1900 Å. The effective area curve as a

IES concluded Phase 1 commissioning with low-voltage check-out on May 9, 2004 while the ROSINA DFMS electronics performance was validated on May 21, producing spectra as shown in figure 1.

Unforeseen Complex Pointing Profiles with MIRO To map the MIRO beam profile a unique series of spacecraft maneuvers was executed. The beam profile, a size of approximately 7 x 7 arc min, required scans of an area of approximately 1 square degree. MIRO had originally proposed several different scan patterns, including the raster scan with which to obtain a calibration signal from the Earth. The project felt that the spacecraft was not sufficiently well characterized this early in the commissioning timeline to perform either the raster scans or any of the other suggested techniques. The concern was the Figure 1 – Acquired mass spectra of the ROSINA stopping and starting of the spacecraft at the end of each Double Focusing Mass Spectrometer (DFMS) taken on raster scan. The only option was continuous spiral scans, a May 21, 2004. unique technique and one applicable only to the MIRO instrument. The technique is illustrated in figure 2 as it applied to the Earth measurement. Input to the navigation team included the spiral pitch (spacing between the scans) and the number of revolutions. The comparison with a standard raster pattern is that scan lines are moved closer together with multiple spirals. Each successive scan improved the spatial density in which the 1 square degree could be scanned and consequently improved the capability to map the response function of the MIRO instrument. Multiple scans improved the signal-to-noise and provided redundancy.

To employ this technique and validate the beam profile, data were taken on Earth on April 24. The starting points mapped out an equilateral triangle with the Earth positioned in the center. The configuration placed the Earth in a different location on each spiral scan. The scans commenced close to the position of the Earth to keep Earth close to the center of the scanned area. Data were taken continuously until three scans were complete. There was no particular rationale for the choice of three scans (it could have been 5 or 1). There was nothing unique about the starting configurations. The Earth signal was detected in each of the three scans, providing redundancy in the process. Steps one through two of the process are outlined below.

Step 1: The spacecraft Z axis (nominal boresight direction of the spacecraft) performs a spiral scan on the sky in the vicinity of the earth. The spiral spacing is approximately half the response pattern of the MIRO telescope. The full scan covers approximately 1 square degree. (In practice, three spiral scans were used, each starting at a different position in the sky. It takes about 1 hour to perform one spiral scan, and three hours to complete the measurement.)

The projection of the X-Y axis on the sky at each point shows up clearly in both of these panels. in time defines a reference frame relative to the nominal Incident’s, Surprises, and Anomalies (ISAs) pointing direction x=y=0. The MIRO beam is fixed in The project keeps a record of mission incidents, surprises, the X-Y reference frame. As the spiral scan proceeds, and anomalies. These are known collectively as ISAs. For the Earth moves around in x-y reference frame and this period of performance, very few problems would fall serves as a source of emission for the MIRO beam. into the category of an anomaly. Most of the instrument When the Earth is in the MIRO beam the MIRO issues fall under the category of surprises. Such surprises radiometer responds with an increased intensity. are cataloged nonetheless. In this section we provide a

sampling of instrument ISAs. Step 2: As the spacecraft Z axis approaches Earth, the MIRO radiometer responds with an increase in Alice Pyro — Upon command to open the ALICE detector intensity. The increase in intensity is mapped onto an door (a one time only mission event), the primary pyro X-Y contour map (as shown in the first panel along the circuit failed to fire. Alice halted commissioning to bottom of figure 2) with intensity the 3rd dimension (as determine the cause of failure. After more than one day, shown in the peak displayed in the second panel, along when insufficient telemetry had been obtained to determine the bottom of figure 2). As expected, the map does not the root cause, it was ascertained that the secondary pyro reach a maximum at x=0 and y=0 because the MIRO circuit should be fired, and the detector door was beam is not exactly aligned with the nominal spacecraft successfully opened. The cause was ultimately determined boresight. The MIRO beam is approximately 5 arc to be a short in the A-side firing lines. minutes away from the spacecraft boresight.

Alice Timing — Alice telemetry exhibited behavior Figure 2 presents the 3D representation of the contour map. consistent with the drift of its internal clock by -1.8 seconds It shows the shape of MIRO beam as well as the offset from per hour. Once the problem was confirmed, a software x=y=0.0 (first and second panels from the left along the patch uploaded to the instrument fully corrected the bottom of figure 2). The noise level of the instrument also

Figure 2 – MIRO pointing strategy for the Earth calibration. The MIRO instrument and its position on the spacecraft are both shown in inserts in the figure. The second panel along the bottom of the figure shows the beam response when the Earth is9 detected.

problem.

IES Temperature — The IES temperature approached the operating limit (58 C) as the spacecraft trajectory carried it 5. OBSERVATIONS OF COMET C/2002 T7 inside 1 AU, and some low-voltage operations were temporarily postponed. The high temperatures were somewhat unexpected but mainly attributable to a poorly (LINEAR) calibrated spacecraft thermal model and proximity to the Sun. A higher than expected temperature at the HGA motor A successful LINEAR observation with Rosetta would be was noticed, and the spacecraft was tilted from the nominal among the closest space-based observations of a comet ever angle to shade the motor with the dish. That step resulted in conducted; however, with spacecraft commissioning in a higher than nominal solar flux on IES, increasing its progress, squeezing in a set of sciences observation was temperature. The temperature increased further when IES problematic. The Project wanted to use the recently was operated, but it never exceeded the safe limit. Once the validated boresight pointing of MIRO to drive the pointing problem was confirmed, low-voltage operations were requirements for this exercise. On April 30, however, the resumed and completed inside the period of Commissioning comet signal was expected to be doppler shifted out of the Phase 1. MIRO range. For this reason, the project scheduled a second opportunity on May 14 when the comet signal was MIRO CTS — A potentially significant problem took place expected to be in MIRO's range. Other remote sensing with the MIRO chirp transform spectrometer (CTS) after instruments riding along with this observation included the Venus observations on April 1. The CTS is the primary Alice, OSIRIS, and VIRTIS, but the pointing specifications spectral detector of the instrument. After a scan, the for these instruments remained to be validated. This meant telemetry bus’ “busy” signal remained engaged, causing the that on April 30, use of MIRO's pointing requirements MIRO fault protection software to switch the instrument to necessarily implied that the comet might not fall into the engineering telemetry. Diagnostics found inverted other instrument’s fields of view, and a MIRO signal might parameters for the CTS in the project database. Upon not be obtained because the comet was out of range. On correction of these inverted parameters, and re-command of May 14, the second opportunity for an attempted the CTS to a science from an engineering mode, MIRO has measurement, a signal from all these instruments might be operated flawlessly. Ground assessment continues. obtained. The problem there was that May 14 fell inside an important spacecraft maneuver window, the first of a ROSINA DFMS High Voltage — Upon initial command of limited number of trajectory maneuvers for the spacecraft the power supply to the DFMS, the nominal output of 3 KV that keep the spacecraft on course for the prime mission, for the transfer optics subsystem power supply caused with a window that spanned May 11-15. The rationale for shutdown rather than activation of the circuit. During prohibiting science observations inside a trajectory investigation, when re-set to 2 KV, the circuit operated maneuver window includes the residual effects of the normally. A new set of voltages were found with the help of burning of engines, and potential problems with arcing if the DFMS reference model which allows to run the DFMS instrument high voltages are powered on. As it turned out, transfer optics subsystem at 1 kV while maintaining the the trajectory maneuver executed successfully and early, performance. thus a second opportunity presented itself for science

Figure 4 – Acquired EUV/FUV spectrum of comet Linear taken by ALICE on 30 April 2004.

WATER OBSERVED IN COMET LINEAR 2002/T7 OBSERVED APRIL 30, 2004 WITH MIRO/ROSETTA

2.5

FWHM = 3.3 MHZ=1.78 KM/SEC 2 T ANT = 1.14 K CTS FREQ=1384.147 MHZ+- ??? REST FREQUENCY 556.936 GHZ 1.5

0.5

-0.5

-1

-1.5

-2 850 900 950 1000 1050 1100 1150 1200 1250 1300 1350 CHANNEL NUMBER

Figure 3 – Acquired MIRO water spectrum of comet Linear taken on 30 April 2004. measurements at a better time for the science instruments commissioning activities to date and are operating involved. nominally. Subsequent to the drafting of this report, IES successfully completed its commissioning and demonstrated The MIRO Linear data were primarily of interest because its capability to measure the solar wind ions and electrons. they validate the MIRO instrument in close to actual Two IES channels that were noisy in ground calibrations operational conditions. The data from MIRO can be used to cleared up significantly with spacecraft outgassing. MIRO determine the water production rate of the comet at one and Alice successfully participated in the Interference point in its orbit. This is of limited scientific interest by Campaign, and Alice conducted stray light tests that showed itself, but it provides an excellent illustration of the MIRO the instrument to be less susceptible to stray light than capabilities. When combined with measurements made with previously expected. other ground-based and spacecraft instruments, the MIRO data will help to define how the water production rate varies as the comet moves around the sun. The actual returned MIRO measurement is shown in figure 3. MIRO was able to detect the comet successfully during both opportunities.

ALICE successfully observed comet Linear on both 30 April 2004 and 14 May 2004. Figure 4 shows the acquired spectrum of the comet’s nucleus region taken on 30 April 2004 at a Rosetta spacecraft to comet distance of 16 million kilometers. H Lyman α and β were detected at 1216 Å and 1025 Å, respectively; in addition, oxygen at 1301 Å and carbon at 1561 Å and 1657 Å were also detected. Initial rate estimates for these emissions closely match that expected for this comet at the heliocentric range at the date of these observations (Feldman 2004 – private communication, [9]), and excellent validation of the Alice experiment.

6. SUMMARY OF POST-LAUNCH OPERATIONS

WITH THE U.S. ROSETTA PROJECT

Instruments in the U.S. Rosetta Project seem very ready for prime mission operations at comet Churyumov- Gerasimenko. The instruments have completed all

REFERENCES BIOGRAPHY

[1] Slater, D.C., S.A. Stern, T. Booker, J. Scherrer, M.F. Dr. Claudia Alexander is currently a Research Scientist at A'Hearn, J.L. Bertaux, P.D. Feldman, M.C. Festou, and the Jet Propulsion Laboratory, O.H.W. Siegmund, “Radiometric and calibration where she serves as both performance results of the Rosetta UV imaging Project Manager and Project spectrometer ALICE,” in UV/EUV and Visible Space Scientist of the US Rosetta Instrumentation for Astronomy and Solar Physics, SPIE Project. She has also served as Proceedings, 4498, 2001. Project Manager of the historic Galileo Mission to Jupiter in the [2] Slater, D.C., J. Scherrer, J. Stone, M.F. A'Hearn, J.L. final last days of the mission. Dr. Bertaux, P.D. Feldman, and M.C. Festou, “Alice-The Alexander is an interdisciplinary Ultraviolet Imaging Spectrometer Aboard the Rosetta scientist. She is currently at work Orbiter,” in ESA SP-1165, 2001. on a model of the rarefied atmosphere surrounding Jupiter's moon Ganymede. She completed a Ph.D. in 1993 in Space [3] S.A. Stern, D.C. Slater, W. Gibson, J. Scherrer, M.A. Plasma Physics at the University of Michigan. Dr. A'Hearn, J.L. Bertaux, P.D. Feldman, and M.C. Festou, Alexander received a Bachelor's Degree from the University “ALICE: An Ultraviolet Imaging Spectrometer for the of California at Berkeley in 1983, and a Master's Degree Rosetta Mission,” Advances in Space Research, 21, 1998. from the University of California at Los Angeles in [4] S. Gulkis, M. Frerking, M. Janssen, P. Hartogh, G. 1985. Beaudin, T. Koch, Y. Salinas, and C. Kahn, "Microwave Instrument for the Rosetta Orbiter," in ESA SP-1165, Dr. S. Alan Stern currently 2001. serves as the Executive Director of the Space Science and Engineering Division of [5] H. Balsiger, K. Altwegg, E. Arijis, J.L. Bertraux, J.J. Southwest Research Berthelier, P. Bochsler, G.R. Carignan, P. Eberhardt, L.A. Institute’s Boulder campus. Fisk, S.A. Fusilier, A.G. Ghielmetti, F. Gliem, T.I He is a planetary scientist and Gombosi, E. Kopp, A. Korth, S. Livi, C. Mazelle, H. astrophysicist with both Reme, J.A. Sauvaud, E.D. Shelley, J.H. Waite, B. Wilken, observational and theoretical J. Woch, H. Wollnik, P. Wurz and D.T. Young, “Rosetta interests. His research has focused on studies of the Orbiter Spectrometer for Ion and Neutral Analysis - satellites of the outer planets, Pluto, comets, the Oort Cloud ROSINA,” Advances in Space Research, 21, 1998. and Kuiper Disk, and tenuous planetary atmospheres. Dr. Stern has over 20 years of experience in space remote [6] J.L. Burch, W.C. Gibson, T.E. Cravens, R. sensing instrument development, with a strong Goldstein, R.N. Lundin, J.D. Winningham, D.T. concentration in ultraviolet and imaging technologies. Dr. Stern is a PI in NASA's UV sounding rocket program. He Young, and C.J. Pollock, “IES – RPC : the Ion and has participated as a project scientist and later PI on two Electron Sensor in the Rosetta Plasma Consortium,” in Shuttle mid-deck experiments spanning four flights, and a ESA SP-1165, 2001. Shuttle-deployable satellite. In 1993, he was PI of the miniaturized HIPPS Pluto breadboard camera/IR [7] P. Ferri and M. Warhaut, “First In-Flight Experience with spectrometer/UV spectrometer payload. In 1996 he became Rosetta”, IAC-04-IAF-Q.5.03, International Aeronautics PI of NASA’s Alice UV spectrometer aboard the Rosetta Congress, Vancouver, Canada, 2004 comet orbiter mission. In 2001 he became PI of NASA’s New Horizons Pluto-Kuiper Belt mission. He has two [8] Consultative Committee for Space Data Systems, Space bachelor’s degrees, two Masters degrees, and a Ph.D. in Link Extension Services - Executive Summary, CCSDS Astrophysics and Planetary Science from the University 910.0-Y-1, YELLOW BOOK - April 2002 of Colorado in 1989.

[9] P.D. Feldman, private communication, 2004 Dr. Raymond Goldstein is currently a Staff Scientist at the The research described in this publication was carried out at Southwest Research Institute. the Jet Propulsion Laboratory, California Institute of While there he has been involved Technology, under a contract with the National Aeronautics in analysis of Cassini/CAPS and and Space Administration. DS-1/PEPE flight data, laboratory calibration of the Rosetta/IES instrument and as its project 12

manager, and in the design of several flight instruments. Solar and Space Physics (2000-2004). He was Principal Prior to that he was a staff scientist at the Jet Propulsion Investigator for the Dynamics Explorer 1 High-Altitude Laboratory. He received a B.S. degree in Physics from City Plasma Instrument and the ATLAS-1 Space Experiments College of New York, New York, N.Y., and a Masters and with Particle Accelerators (SEPAC). Currently, he is Ph.D. degree in Physics from Lehigh University, principal investigator for the Ion and Electron Sensor for the Bethlehem, Pennsylvania. In his career at JPL he was European Space Agency ROSETTA comet orbiter and for a responsible (as Co-Investigator) for prototype design and NASA Medium Class Explorer (MIDEX) mission: Imager laboratory calibration of the ion mass spectrometer flown for Magnetopause-to-Aurora Global Exploration (IMAGE), past comets Halley and Grigg-Skjellerup on the Giotto launched in March 2000. Dr. Burch was the AGU Van spacecraft and has been actively involved in the analysis of Allen Lecturer and the Rice University Marlar Lecturer, data from these encounters, particularly regarding cometary both in 2001. coma composition and the dynamics of the interaction of the solar wind with the coma.

Dr. Stephen Fusilier is presently Dr. David Slater is a Principal Scientist at Southwest Manager of the Space Physics Research Institute where he serves as the Project Scientist for the Rosetta ALICE instrument. Dr. Slater is also serving Department at Lockheed Martin as a Co-Investigator for the ALICE UV instrument on the Advanced Technology Center NASA New Horizons mission (approximately 40 scientists and to Pluto/Charon and the engineers). He previously served as Kuiper Belt scheduled for Group Leader for the Space launch in January 2006. His Plasmas. He has served as Co-I on main interests involve the Imager for Magnetopause to Aurora design and development of Global Exploration (IMAGE), and detectors and remote sensing Co-I on the Rosetta ion and neutral mass spectrometer and instruments for space science the Simple Plasma Experiment for the RoLand lander. He missions and ground-based serves as the Lead US Co-I on the Rosetta orbiter astronomy. In addition, he is spectrometer for ion and neutral analysis (ROSINA), interested in EUV/FUV developing instrumentation for a rendezvous with a comet. spectroscopy of planetary He assisted in the calibration of the GIOTTO ion mass atmospheres and solar physics. Dr. Slater received his Ph.D. spectrometer and analyzed data from the GIOTTO in 1991 in Applied Physics at Stanford University. He encounter with comets Halley and Grigg-Skjellerup. He has received his Bachelor’s Degree in Physics at the University been responsible for analysis of space plasma data from the of California, Los Angeles in 1979, and a Master’s Degree ISEE, ICE, AMPTE/CCE, POLAR and IMAGE spacecraft, from the Air Force Institute of Technology in 1980. CRRES chemical releases, and AEPI artificial aurora experiment. He was Project Manager for the LMMS Dr. James L. Burch is Vice- participation in the Imager for Magnetopause to Aurora President of the Space Science Global Exploration (IMAGE) mission and the LMMS and Engineering Division at participation in the Rosetta Orbiter Spectrometer for Ion and Southwest Research Institute in Neutral Analysis (ROSINA) experiment. He has published San Antonio, TX. He received over 170 papers in scientific journals and conference his B.S. in Physics in 1964 from proceedings. St. Marys University of Texas and his Ph.D. in Space Science Dr. Samuel Gulkis has from Rice University in 1968. over 35 years of research

Dr. Burch is a fellow of the experience in radio and American Geophysical Union. He has served as a member submillimeter astronomy, of the NASA Space Science and Applications Advisory specializing in studies of Committee (1990-1993) and the Space Physics Jovian magnetospheric Subcommittee (1991-1994) and has chaired the Sun-Earth physics, the major planet Connection Strategic Planning Integration Team (1996- atmospheres, and

1997). He has also served as president of the Space Physics experimental cosmology. and Aeronomy Section of the AGU (1996-98) and is a He has served as Co- Member of the International Academy of Astronautics. Dr. Investigator on two NASA space experiments (COBE and Burch has served as Editor and Editor-in-Chief of Voyager), and is currently the Principal Investigator of the Geophysical Research Letters (1988-1993). He served as MIRO-ROSETTA experiment, currently under chair of the AGU Committee on Public Affairs (2001-2003) development by the European Space Agency. He has served and chair of the National Research Council Committee on 13

on numerous NASA Advisory Committees on Planetary and Dwight Holmes is currently at the Jet Propulsion Space Astronomy, and has served on the Icarus Board of Laboratory where is serves as the Telecommunications and Editors. He received two NASA Exceptional Scientific Mission Services (TMS) manager for Rosetta. Mr. Holmes Achievement Awards, one for work on Outer Planet is also the current TMS manager for two other NASA/ESA Models, the other for work on Observational Cosmology. cooperative missions, INTEGRAL, and Mars Express. Mr. He was appointed Senior Research Scientist at JPL in 1981. Holmes has also served as the TMS manager for the launch Dr. Gulkis has managed planetary atmospheres, space and early operations of NASA’s Genesis and Stardust physics, planetary and life detection and astrophysics missions. Early in his career at JPL Mr. Holmes served as research groups in the Earth and Space Sciences Division, the Radio Science team chief for the Voyager dual mission and served as the Program Scientist for Solar System to the outer planets, and as the Radio Science team chief in Exploration in the Space and Earth Science Program the early mission development phase of the Galileo Directorate. program. He completed his Master’s Degree in Space Science and Applied Physics at Johns Hopkins University Dr. Joel Parker’s research involves photometric and in 1978, the same year he began work at JPL. Mr. Holmes spectroscopic multi-wavelength studies in planetary and received his Bachelor’s degree in Electrical Engineering stellar astrophysics using ground- and space-based, from Rutgers University, New Brunswick, New Jersey, in instruments. He is the Operations 1968. Scientist and Project Manager for the Alice UV spectrometer on the William C. Gibson is Assistant Vice-President, Space Rosetta mission, and data Science and Engineering Division, Southwest Research processing and archiving lead on Institute. He has extensive experience in the management of both the Alice-Rosetta and Alice- projects involving the development of scientific instruments New Horizons projects. His topics and support systems for use on the Space Shuttle, free of interest include asteroids, flying satellites, sounding comets, Centaurs and Kuiper Belt rockets, and high-altitude objects, Pluto, the Moon, research balloons. Mr. Gibson vulcanoids, local group galaxies, young stellar groups and has managed such projects as their environments, initial mass functions and star-formation the SEPAC Interface Unit for rates, interactions of massive stars with the ISM, luminous Spacelab Mission I, the High blue variables, and data reduction and analysis techniques. Altitude Plasma Instrument for He received a B.A. in Physics and Astronomy at the the Dynamics Explorer University of California, Berkeley, in 1986, an M.S. in Satellite, the Fast Ion Mass Astrophysics at the University of Colorado, Boulder, 1989, Spectrometer for the Centaur and a Ph.D. in Astrophysics at the University of Colorado, Rocket Project, and the Boulder, in 1992. Balloon-Borne Ultraviolet Stellar Spectrometer. In addition to these projects, he has John Scherrer is currently a served as the project manager for the Imager for Senior Program Manager at Magnetopause-to-Aurora Global Exploration (IMAGE) Southwest Research Institute, Medium-Sized Explorer (MIDEX) mission and is the where he serves as the Project project manager designee for the Waves Explorer MIDEX Manager for the New Horizons mission. His areas of technical specialization include the Alice ultraviolet imaging design of spacecraft data systems, spacecraft telemetry and spectrometer delivered for control systems, and spacecraft heat transfer systems. Mr. spacecraft integration in Gibson was the architect of the multiprocessor SEPAC On- September 2004. Mr. Scherrer Line Data Analysis (SODA) real-time telemetry ground also served as the Project station used during STS-9 and the lead-design engineer on manager of Rosetta Alice during the Johnson Space Center Stratospheric Ozone Experiment. the development phases of that instrument. Mr. Scherrer Mr. Gibson has served as a member of NASA source was the deputy project manager/spacecraft manager for selection boards and as chairman of the NASA NASA’s first MIDEX mission, IMAGE, launched in March Confirmation Review Board for the GALEX Small 2000 and the Project Manger of Mars Express ASPERA-3, Explorer mission. Mr. Gibson also served as a member of the NASA Discovery office’s first Mission of Opportunity. the standing review board for the Mr. Scherrer received a Bachelor’s degree from Texas NASA Advanced Composition A&M University in 1982 Explorer (ACE) mission. He is a and a Masters degree from member of the NRC Task Group the University of Texas at on the Principal Investigator-led San Antonio in 1986. Earth Science Mission.

Dr. Tamas I Gombosi is Professor and Chair of the Department of Atmospheric, Oceanic and Space Sciences at the University of Michigan. His research interests include space plasma physics, planetary science and space weather. He received his M.S. and Ph.D. degrees from the Lóránd Eötvös University at Budapest, Hungary. He is a lifetime elected member of the International Academy of Astronautics, Fellow of the American Geophysical Union, member of the American Physical Society, the American Astronomical Society and recipient of nine scientific awards. Contact him at [email protected].